Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$96.52	13.499%	$109.5492	$109.55	$109.55	$109.50
Purchase #2	$90.65	3.585%	$93.8998	$93.90	$93.90	$93.90
Purchase #3	$30.45	5.427%	$32.1025	$32.10	$32.10	$32.10
Purchase #4	$11.82	11.141%	$13.1369	$13.14	$13.15	$13.10
Purchase #5	$195.96	4.846%	$205.4562	$205.46	$205.45	$205.50
Purchase #6	$46.29	4.770%	$48.498	$48.50	$48.50	$48.50
Purchase #7	$171.63	5.652%	$181.3305	$181.33	$181.35	$181.30
7 purchase totals =	$643.32		$683.9731	$683.98	$684.00	$683.90